Drastic reduction in air pollution may decrease CVD risk

By identifying the positive health effects of a reduction in air pollution exposure, a new NIEHS-funded study led by Junfeng (Jim) Zhang, Ph.D., a professor in the Keck School of Medicine at the University of Southern California (USC), shows how air pollution contributes to cardiovascular disease (CVD) risk.

“We believe this is the first major study to clearly demonstrate that changes in air pollution exposure affect cardiovascular disease mechanisms in healthy young people,” said Zhang.

This environmental health research, with real-world conditions, was possible because the Chinese government agreed to temporarily improve air quality in Beijing, as a stipulation for hosting the 2008 summer Olympic Games. To clean up Beijing for the Olympic Games in China, factories were closed down and car traffic was limited. This governmental air quality intervention set the stage for a controlled examination of pollution-mediated health effects.

“Beijing is one of the most polluted cities in the world,” said Zhang. “We wanted to take advantage of such a huge intervention and look at what happens to people biologically.”

Seizing the unique opportunity to gauge changes in air quality, a team led by Zhang measured air pollutants before, during, and after the Olympic Games. At the same time, the researchers also measured seven markers of cardiovascular health in 125 healthy, non-smoking, young people, who were an average of 24 years old. Several blood plasma factors, cell counts, blood pressure, and heart rate were examined.

Air pollution exposure linked to risk for cardiovascular disease

During the Games, air pollutant concentrations decreased substantially. These air quality improvements were associated with improved biological measurements in the young adults, indicating decreased risk for cardiovascular problems. However, when industrial and automotive activity resumed in Beijing, the cardiovascular health indicators returned to high-risk levels.

Thus, the short-term reduction in air pollution levels during the games led to temporary improvement in cardiovascular health among study participants.

Although the research did not quantify the risk from air pollution exposures, it provides invaluable information for improving the assessment of public health impacts of air pollution reduction.

Public health impacts

During the past two decades, both chronic and short-term air pollution exposures have been related to cardiovascular diseases in numerous observational studies. But few studies have examined how the environment affects disease pathways. Through the investigation of biological indicators clinically related to cardiovascular morbidity or mortality, the work of Zhang’s research team stands apart.

According to the American Heart Association, air pollution can trigger heart attacks and other heart problems, especially in people with underlying cardiovascular conditions. This new study shows that even healthy people, like the young adult participants, may experience cardiovascular disease symptoms from exposure to elevated levels of air pollution. In the United States, more than 40 percent of people live in areas where air pollution threatens their health, according to the American Lung Association State of the Air 2012 report.

Large numbers of people around the world are exposed to air pollution levels as high as Beijing’s, explained Jonathan Samet, M.D., director of the USC Institute for Global Health.

Zhang and fellow authors maintain that their findings further provide data to support the argument that air pollution may be a global risk factor for cardiovascular disease.